Device for manufacturing tobacco webs and sheets



July 5, 1966 R. JANSSON 3,259,136

DEVICE FOR MANUFACTURING TOBACCO WEBS AND SHEETS Filed April 1, 1965 FIG 2 FIG 3 1 NVEN TOR Ragnar Jansson BYWOZQLOMM ATTORNEYS United States Patent 90 3 Claims. (Cl. 131-133) This application is a continuation-in-part of my application Serial No. 162,798 filed December 28, 1961, now abandoned, entitled Device for Manufacturing Tobacco Webs and Sheets.

This invention relates to a device for manufacturing tobacco webs or sheets from a paste of tobacco which paste is transferred in the form of a thin layer to a conveyor belt, by means of a casting roll, to be dried and possibly further treated.

In known devices of this kind wherein th surface of the casting roll is in contact with a paste, comprising tobacco powder admixed with aqueous solutions of binding agents, in a container, and wherein the casting roll cooperates with a doctor roll or doctor blade to provide a layer of tobacco paste having a desired thickness on the surface of the casting roll, said layer is generally directly transferred to a conveyor belt, arranged beneath the casting roll and in contact with same as disclosed in US. Patent No. 2,747,583. In such case a bunch of tobacco paste is formed in the pocket between the conveyor belt and the surface of the casting roll so that the thickness of the layer transferred to the belt will vary such that special smoothing means must be provided. Such variations in the thickness of the tobacco web produced are further caused when the casting roll is not truly circular in section and by vibrations in the conveyor belt, whereby the mass of tobacco paste in the pocket between the casting roll and th belt will vary in dependence on, for example, the said vibrations.

The object of the invention 'is to overcome said disadvantage, and this is achieved by providing a wiper blade or the like arranged in the spacing between the casting roll and the conveyor belt, where the surface of the casting roll moves in a direction opposite to that of the conveyor belt, which wiper blade operates on the surface of the casting roll and has its wiper edge directed opposite to the direction of movement of the casting roll to guide the layer of tobacco paste from said surface, whereby the spacing between the casting roll and the conveyor belt exceeds the thickness of the edge of the wiper blade contacting the casting roll, so that the layer will be freely transferred to and caught by the conveyor belt.

The risk that a bunch of tobacco paste will be formed between the casting roll and conveyor belt is, thus, positively overcome, so that variations in the distance between the belt and the surface of the roll, resulting from, for example, belt vibrations will not noticeably affect the thickness of the layer of tobacco paste. The invention will now be described in greater detail by way of example with reference to the accompanying drawing, which diagrammatically illustrates an embodiment of the invention. In the drawing:

FIGURE 1 illustrates the principles of the exemplary embodiment,

FIGURE 2 shows the wiper blade and fragments of the members cooperating with same in an enlarged scale, and

FIGURE 3 is a detail view similar to FIGURE 2 with a modified wiper blade.

Referring to FIGURE 1 there is shown a container 1 for tobacco paste, a casting roll 2 which is partly in contact with the tobacco paste in the container 1, and a doctor roll 3 which has part of its surface in contact with ice the paste in the container 1. Between the casting roll 2, which is rotated by driving means (not shown) in the direction indicated, and the doctor roll 3, which is rotated by driving means (not shown) in the direction indicated, is a narrow spacing determining the thickness of the layer 8 of tobacco paste transferred from the container 1 to the peripheral surface of the casting roll 2. A conveyor belt 4 made, for example, of stainless steel runs below the casting roll 2. The upper part of the conveyor belt 5 runs from th left to the right over support rolls 5, only one of which is shown.

As is best shown in FIGURES 2 and 3 the conveyor belt 4 is lotcated at such a distance from the lowermost point on the casting roll 2 that the layer 8 transferred from the casting roll 2 by the wiper blade 6 is guided to the conveyor belt 4 without any risk that the layer on the casting roll 2 will contact the layer on the conveyor belt 4, so that a bunch of clogged tobacco paste in the pocket between the roll 2, blade 6 and belt 4 is positively prevented.

A tobacco paste sheet in wet condition, i. e. a sheet which has not been dried and in which the binder, for example a cellulose, does not constitute a supporting film or the like, is extremely diffi-cult to handle and cannot be subjected to tension. This means that the sheet formed on the roller 2 after being removed from th roller surface by the doctor blade 6 must not hang down from the doctor blade edge in which case the sheet will be torn oil, but must be supported as soon as possible by the conveyor belt 4 as shown in FIGURES 2 and 3.

According to the invention, the distance between the roller 2 and belt 4 has been chosen such that the tobacco paste sheet in the spacing between the roller and belt constitutes a pillar supported by the edge of the doctor blade 6, the belt 4 and the roller 2 and, thus, the freely hanging sheet has been made as small as possible, which means in turn that the tension forces acting on the web in the spacing are minimized. All this can also b expressed so that the space between the under side of the doctor blade 6 and the surface of the belt 4 is as small as possible in dependence on the thickness of the tobacco web 8 relative to the thickness of the edge of the doctor blade 6. To avoid clogging, i.e. to :avoid that the web removed from the surface of the roller 2 engages the web transferred to the belt 4 a certain distance must be provided between the lowest point of the roller 2 and the belt 4.

The said distance between the casting roll 2 and the conveyor belt 4 may vary within limits determined by the specificchanacteristics of the tobacco paste layer 8. It has turned out that the lower limit substantially is a function of the thickness of the tobacco paste layer 8 and the minimum distance between the point on the roll sunface closest to the conveyor belt surface and is pref erably 2.5 to 3 times the thickness of the tobacco paste layer 8, which means that there will be a spacing between the layer 8 adhering to the roll surface and the layer already transferred to the belt 4 about equal to the thick ness of the tobacco layer 8. The thickness of the Wi'per blade 6 should be such as to prevent the blade 6 from contacting the belt 4, thereby allowing the layer 8 removed from the roll 2 to freely slip down on the conveyor 4.

The upper limit of the 'value of the said distance depends substantially on the tension strength of the pasty layer 8, which in turn depends on the thickness of the layer and on the tobacco paste composition.

As the tensile strength of the pasty layer 8 is comparatively small any considerable gravity forces acting on that part of the layer 8 which is being transferred from the the roll 2 to the conveyor 4 cannot be allowed. It has, thus, been found that the maximum distance between the point on the roll 2 closest to the conveyor belt 4 is about 6.0 turn. when working with a tobacco paste consisting of the following relative amounts: 25 grams of ground tobacco, 4.45 grams of carboxymethyl cellulose (CMC) as binder and some other components, which other components do not affect the tensile strength and, thus, are of no interest in this case. A layer 8 having a thickness of 0.5 mm. was formed from this composition and with a 6.0 mm. spacing a satisfactory layer 8 was transferred to the conveyor belt 4. If the distance between the roll 2 and the conveyor belt 4 was increased to 7 mm. the thickness of the layer 8 on the conveyor belt was uneven and at a further increase to 9.0 mm. defects in form of holes occurred in the layer 8 on the belt 4. With the said tobacco paste composition and the said thickness of the layer 8 on the roll 2 the best quality of the layer on the belt 4 and thus of the final product was obtained with a spacing of 2.0 to 3.0 mm.

It should, however, be noted that the above upper limit depends on the characteristics of the tobacco paste and on variation in the speed of the conveyor belt. If the tobacco paste contains long fibers and a large amount of binder it is possible to increase the said distance up to 15 mm. provided, however, that vibrations in the conveyor belt 4 can be neglected.

If the conveyor belt speed varies or vibrations occur the distance must be decreased accordingly to avoid defects in the layer 8 on the belt 4.

As it is almost impossible to avoid such variations and vibrations the maximal spacing for practical use is about 11.0 mm. for the strongest types of tobacco paste, i.e. paste containing a large amount of long fibers and a suitable amount of binder.

Preferably the wiper blade 6 is provided with an edge abutting the surface of the casting roll 2 in a plane through the axis of the roll 2, which plane is substantially perpendicular to the plane of the conveyor belt 4. As is diagrammatically shown in FIGURE 1 the thrust force between the wiper blade 6 and the roll 2 can be conveniently adjusted by an adjusting screw 7. Since the roll 2 can be made of, for example, stainless steel a considerable thrust force between the edge of wiper 6 and roll 2 can be obtained to ensure a reliable transfer of the layer 8 from the casting roll 2. The wiper blade 6 may possibly be caused to oscillate, preferably laterally by convenient driving means .to facilitate the transfer of the layer 8 from the edge of the Wiper blade 6 to the belt 4.

FIGURE 3 illustrates a modified wiper blade 16 with a knife-shaped edge. As indicated in the figure this blade is a composite blade consisting of an upper blade half 6' of a plastic material, as nylon, and a lower blade half 6" consisting of a metallic material, as stainless steel and secured to the upper half. The wiper 6 in FIGURE 2 may also be constructed this way.

Other modifications of the invention are, of course, possible within the scope of the invention and, thus, the invention is not restricted to the embodiments shown.

Iclaim:

1. A device for manufacturing tobacco webs and sheets from a paste of tobacco comprising a casting roll having a casting roll surface, a conveyor belt mounted below and slightly spaced from said roll moving in a direction opposite to that of said casting roll surface adjacent said belt,

a wiper blade having a wiper edge arranged in the spacing between said casting roll and said conveyor belt, the top edge ofsaid wiper blade abutting said casting roll surface in a plane through the axis of said casting roll which is substantially perpendicular to the surface of said conveyor belt adjacent said casting roll, said wiper blade operating on said casting roll surface with said wiper edge directed opposite to the direct-ion of movement of said casting roll surface to guide a layer of tobacco paste from said surface, the spacing between said casting roll surface and said conveyor belt being between 2 mm. and 15 mm. and being sufficiently wide to allow the layer portion adhering to said roll surface at the point closest to said conveyor belt surface to run free from the layer portion already transferred to said conveyor belt, so that the layer of paste will be .freely transferred to and caught by said conveyor belt but not so wide that any substantial tension, due to gravity forces acting on the freely transferred layer portion is imparted to the last mentioned portion.

2. A device for manufacturing tobacco webs and sheets from a paste of tobacco comprising a casting roll having a casting roll surface, a conveyor belt mounted below and slightly spaced from said roll moving in a direction oppo site to that of said casting roll surface adjacent said belt, a blade having a wiper edge arranged in the spacing between said casting roll and said conveyor belt, the top edge of said wiper blade abutting said casting roll surface in a plane through the axis of said casting roll which is substantially perpendicular to the surface of said conveyor belt adjacent said casting roll, said wiper blade operating on said casting roll surface with said wiper edge directed opposite to the direction of movement of said casting roll surface to guide a layer of tobacco paste from said surface, said spacing being between 2.0 mm. and 11.0 mm.

3. A device for manufacturing tobacco webs and sheets from a paste of tobacco comprising a casting roll having a casting roll surtface, a conveyor belt mounted below and slightly spaced from said roll moving in a direction opposite to that of said casting roll surface adjacent said belt, a wiper blade having a wiper edge arranged in the spacing between said casting roll and said conveyor belt, the top edge of said wiper blade abutting said casting roll surface in a plane through the axis of said casting roll which is substantially perpendicular to the surface of said conveyor belt adjacent said casting roll, said wiper blade operating on said casting roll surface with said wiper edge directed opposite to the direction of movement of said casting roll surface to guide a layer of tobacco paste from said surface, said spacing being between 2.0 and 3 .0 mm.

References Cited by the Examiner UNITED STATES PATENTS 1,583,484 5/1926 Morrison et al 18-l55 2,478,885 9/1949 Alvey 18--2 2,566,943 9/1951 King 10()174 2,747,583 5 6 Frankenburg 131140 2,842,092 7/1958 Poniper 131-155 SAMUEL KOREN, Primary Examiner.

MELVIN D. REIN, Examiner. 

2. A DEVICE FOR MANUFACTURING TOBACCO WEBS AND SHEETS FROM A PASTE OF TOBACCO COMPRISING A CASTING ROLL HAVING A CASTING ROLL SURFACE, A CONVEYOR BELT MOUNTED BELOW AND SLIGHTLY SPACED FROM SAID ROLL MOVING IN A DIRECTION OPPOSITE TO THAT OF THE CASTING ROLL SURFACE ADJACENT SAID BELT, A BLADE HAVING A WIPER EDGE ARRANGED IN THE SPACING BETWEEN SAID CASTING ROLL AND SAID CONVEYOR BELT, THE TOP EDGE OF SAID WIPER BLADE ABUTTING SAID CASTING ROLL SURFACE IN A PLANE THROUGH THE AXIS OF SAID CASTING ROLL WHICH IS SUBSTANTIALLY PERPENDICULAR TO THE SURFACE OF SAID CONVEYOR BELT ADJACENT SAID CASTING ROLL, SAID WIPER BLADE OPERATING ON SAID CASTING ROLL SURFACE WITH SAID WIPER EDGE DIRECTED OPPOSITE TO THE DIRECTION OF MOVEMENT OF SAID CASTING ROLL SURFACAE TO GUIDE A LAYER OF TOBACCO PASTE FROM SAID SURFACE, SAID SPACING BEING BETWEEN 2.0 MM AND 11.0 MM. 